The worst insurgent attack in Sinai during that period took place on Aug. 19 when militants pulled 25 police conscripts off minibuses and shot them dead on the side of the road.

The bus bombed Monday was traveling from the border town of Rafah to el-Arish escorted by an armored police car. The bomb was set off by remote control, said the officials, who spoke on condition of anonymity because they were not authorized to speak to the media.

"In light of the security situation and after the acceptance of the government, it has been decided to extend [the state of emergency] for two months," presidential spokesman Ihab Bedawi told CBS News' Alex Ortiz in a phone interview. "The reason behind it is the latest terrorist activities."

Emergency law has already been in effect for a month -- since the bloody crackdown on encampments of Morsi supporters on Aug. 14 -- allowing the government sweeping powers of arrest.

The implementation of emergency law has failed to stem the attacks by Islamist militants, which increased since the pro-Morsi protest camps were broken up.

In two of the most worrying attacks for Egypt's military-backed interim government, the first suicide bombings seen in the country since the Arab Spring-inspired uprising which toppled dictator Hosni Mubarak struck in the heart of the capital, in the form of a failed assassination attempt on Interior Minister Mohammed Ibrahim, and then subsequently in twin blasts targeting military offices in Sinai.

The violence has been worst in the Northern Sinai Peninsula, where militants and security personnel have been battling nearly every day since Morsi's ouster.